(a) Field of the Invention
The present invention relates to an amorphous alloy and a manufacturing method there of, and more specifically to an amorphous alloy with good strength and high corrosion resistance and a manufacturing method thereof.
(b) Description of the Related Art
A fuel cell has been spotlighted as an alternative energy source due to global warming, pollution, and depletion of oil resources. The fuel cell is an electric generator. In the fuel cell, reactants continuously flow into the system while products are continuously discharged from the system. At the same time, electric energy is generated. That is, oxygen and hydrogen are continuously supplied to the fuel cell and a chemical reaction occurs, thereby generating electrical energy.
Various types of fuel cells have been developed. The fuel cells can be classified as high temperature fuel cells and low temperature fuel cells depending on electrolytes in a unit cell and operational temperature. The high temperature fuel cells include molten carbonate fuel cells, solid oxide fuel cells, and so on. The low temperature fuel cells include phosphoric acid fuel cells, polymer electrolyte fuel cells, alkaline fuel cells, and so on.
In particular, a polymer electrolyte membrane fuel cell (hereinafter referred to as a “PEMFC”), one of the solid polymer electrolyte fuel cells (hereinafter referred to as a “SPEFC”) that is a low temperature fuel cell, is compact and light-weight, and has an advantage to be capable of operating at a low temperature. The PEMFC generates electric power from hydrogen and oxygen through a polymer membrane consisting of a membrane electrode assembly (hereinafter referred to as an “MEA”). The MEA is made by combining the polymer membrane with electrodes located on each side thereof.
Each electrode support is made of carbon cloth supporting electrode materials such as carbon black including platinum catalysts. A plurality of the MEAs with a thickness of several tens to several hundreds of micrometers are filled between multi-functional bipolar plates in order to obtain sufficient electric power. Therefore, several tens to several hundreds of unit cells are serially connected to each other and form a fuel cell stack.
The bipolar plates of the PEMFC are exposed to severe operating conditions in which current and stress are applied and corrosion occurs. Therefore, materials for the bipolar plates are required to have properties of gas impermeability, high strength, corrosion resistance, and good electrical conductivity. Currently used bipolar plates mainly made of a carbon do not have such properties. In particular, thin metallic bipolar plates with high strength and low cost are required since bulk graphite bipolar plates are weak.
Therefore, research relating to bipolar plates made of graphite composites and stainless steels as a replacing material of the bipolar plates has been undertaken. In addition, as a method of manufacturing bipolar plates, research relating to a thermal nitriding surface treatment, TiN coating on stainless steel, thin PVD (physical vapor deposition) coatings, etc., has been pursued.
However, there is a problem in that metallic ions are dissolved and the MEA is poisoned if the electrons are lost in the bipolar plates. Furthermore, metallic oxides grow in a cathode since the metallic bipolar plates obtain electrons and then a recovery reaction occurs. Therefore, there is a problem in that electrical resistance of the surface increases while performance of the fuel cell is deteriorated. Materials with high strength and corrosion resistance have been seriously required in other circumstances in addition to materials for the fuel cells.